Electric coupling



A. ALLAN ELECTRIC COUPLNG Filed Jan, l0, 1950 April 7, 1931.

Patented Apr. 7, 1931 UNITE STATES PATENT OFFICE ARCHIBALD ALLAN, OF TYNEMOUTH, ENGLAND, .ASSIGNOR T A. REYROLLE & COM- PANY LIMITED, OF HEBBURN-ONTYNR ENGLAND, A REGISTERED COMPANY 0F GREAT BRITAIN ELECTRIC COUPLING Application filed January 10, 1930, Serial No. 419,985, and in Great Britain February 19, 1929.

This invention relates to electric couplings of the kind often used in switch gear wherein a conductor terminating say in a plug or socket and surrounded by a hollow yporcelain or like ins-ulator itself surrounded by a metal casing, operates in conjunction with another conductor usually vmounted in an insulating bushing and terminating in a socket or plug.

In such couplings various arrangements have been suggested to prevent excessive electrostatic stress in the solid or other insulatinor materials or media or to equalize or distribute such stresses evenly with a View to preventing breakdown or corona discharge at high voltages. In one such arrangement arecessed portion or neck of the insulator Surrounding one conductor has been surrounded by a metal band or sheath in electrical contact with the conductor.

The present invention has forv its obj ect the construction of a coupling of the general kind above referred to wherein the prevention of the excessive electrostatic stress is very effectually provided for.

In an electric coupling according to this invention the hollow or orifice insulator is surrounded b oil or insulating compound in a metal casing, and surrounding the insulator and in close proximity to the main body of it is a metal shield connected to the conductor on which the insulator is carried, such metal shield extending sufficiently far over the hollow part or orifice of the insu-y lator as to shield the other cooperating conductor and its bushing and confine the electrostatic stress to the oil or compound between the shield and thecasing.

Two constructions of coupling according to the invention will now be described by way of example with reference to the accompanying drawings, in which Figure l shows an elevation `of the coupling with the hollow or orifice insulator in section,

Figure 2 is an elevation on a reduced scale of a modified form of coupling, the hollow or orifice insulator being shown partly in section.

hollow or orifice vinsulator A is bell-shaped and is clamped to a conductor B, which terminates inside the inner end of the insulator in a contact block B1, by means of a nut B2. The contact block B1 cooperates with finger or spring contacts C carried by a metal cap C1 mounted on the end of an insulating bushing D through which the conductor to the contacts C passes.

Surrounding the insulator A and clamped to the conductor B by means of the ring B3 is a metal shield E which is also bell-shaped. The shield E extends in close proximity to the main body of the insulator to a position, as indicated by the broken line El, somewhat below the metal cap on the bushing D and terminates in an internally rounded or beadedv edge E2. The whole arrangement is surrounded by a metal casing F, the space between this casing and the shield being filled with oil or insulating compound.

The arrangement shown in Figure 2 is similar to that of Figure 1 with the exception that the bell-shaped metal shield E is replaced by metallic shield E4 formed on the outer surface of the orifice insulator and connectedY to the insulator clamping nut B2. This metallic shield may be formed by any suitable metallizing process, by painting with a metallic paint or by thin metal foil or wire wound on or otherwise fixed to the surface of the insulator.

In either of the above constructions the electrostatic stress is practically confined to the oil or compound between the shield and the casing and danger from breakdown through undue stress in the air gap within the orifice insulator eliminated.

It will be appreciated that the above description is by way of example only and that modifications may be made in the detailed construction of the arrangement within the scope of the invention. Although the coupling is shown in the drawing in a vertical positioniit is to be understood that the invention is equally applicable to couplings of either the horizontal or the vertical drawout or plug-and-socket type or to couplings inclined at any angle.

Y and aV metallic shield surround-ing and in L Y Vilhat l Vclaim as my invention and desire to secure -by Letters Patent is :-v

l. ln an electric coupling the combinationV of a conductor, a hollow insulator carried VVby and surounding said conductor, a second yconductor cooperating with the first conductor to mak-e and break electrical Contact y therewith, an insulating support or bushing for said second consueto; afinetal-shield connectedv tothe first conductor and closely surroundino' saidV hollow insulator and eX# tending "suiiiciently far over its'surface to shield said second conductor and part ofits bushing, and` outer metal casing sure whole, coupling and separated rounding Lne therei'om'by insulating inedium.- l

2. An electric coupling comprising the combination of a lirst Contact member, afhol low' `insulator Qurroundingl the said member and carriedthereby, a secondcontactniember 'for cooperating with the iirst'vmember,

an insulating" bushing' carrying the second member and arrangedv to be inserted within thehollow insulator to effect the engagerl ment oi the members, a metal fcasingsur-y rounding the hollow insulator, insulating medium between the insulator and? the casing,

close proximity to they insulator, saideshield being connected to the first contactmem-ber and'extending' over the hollow insulator' so as to surround the secondmember and'part of its ybushing* and-to @Online the 'electrof static stress to the insulating! medium be tween the shield andthe casing?.

3. An electric coupling including in kcom#v binationY a conductor, an Yorice insulator carried thereby, a irst contact within the Yinsulator and connected Vto the conductor, a Y

second cooperating contact, an insulating bushing carrying said second contact and adapted to be inserted within the insulator to eil'ect the engagement 'ofthe contacts, an outer iiietal casingsurrounding-the insulater, insulating oil between the casingv andv the insulatoneand a metal shield carried by and closely surrounding the'insulator', said shield extending suiiiciently farV over` the orifice part of the insulator to shield the con-` tacts and part of the bushingand to confine the electrostatic stress to the oil between snield and the outer metal casing.

lntestimony whereof l have signed*l name to this specification.

AnoHiBALD i ALLAN;

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